This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. Our long term project involves the assimilation of pentoses found in agricultural residues into yeast metabolism for conversion into ethanol and other higher value compounds. Since yeast does not have the necessary native enzymes (primarily dehydrogenases/reductases) to do this, we are structurally characterizing these from other organisms to engineer appropriate cosubstrate specificities to allow for cosubstrate recycling in the high flux pathway. We have had success in a prior regular proposal doing this for xylose where we converted an NAD-dependent xylitol dehydrogenase into one with a specificity for NADP and a NADPH-dependent xylose reductase into a NADH-preferring enzyme. The focus has shifted to arabinose now and we are trying to convert an NADPH-dependent L-xylulose reductase into one that utilizes NADH.